Harmonic damper balance weight variations, SBF

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Calypso
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Harmonic damper balance weight variations, SBF

Post by Calypso »

A friend bought a 28oz SBF 302 long block from a reputable builder. Relatively normal performance parts and balanced with the accompanying TCI rattler according to the seller. (Eagle crank, rods, Ross pistons, main cap girdle, Trick Flow hydro roller and heads)

Due to the application, the Rattler could not be utilized as it wasn't the right depth and bolt pattern. It was replaced with Ford performance parts unit with the same balance factor. The engine vibrates noticeably during acceleration. The Rattler has not been messed with in the balance job.

The engine has a small weiand blower, which I'm not familiar with to know If you could test on the engine. That would anyway mean running without blower, alternator and water pump belts.

The next step is to take the dampers to the machine shop to be checked for balance differences. Otherwise there is not much else to do but to take it out, tear it down and send the whole rotating assy to be checked for balance.

The engine didn't come with a flywheel/flexplate.

Anyone seen similar effect from just changing the damper from one manufacturer to another without re-balance? Anything else I could be missing?
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Re: Harmonic damper balance weight variations, SBF

Post by hondo383 »

You'll be time and aggravation ahead just taking it all apart and having it balanced
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Re: Harmonic damper balance weight variations, SBF

Post by BILL-C »

No 2 brands of dampers or flywheels agree on the imbalance weights. We keep a log on the different part# and brands. Brand a is 25 in-oz, and brand b is 30 in-oz for a 28 in-oz application. for external balance apps, if you didn't get the actual damper and flywheel the crank was balanced with, you don't have a properly balanced assembly.
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Re: Harmonic damper balance weight variations, SBF

Post by Scotthatch »

They have both given great advice on balance so not even going to touch on that ...

I did want to comment on the blower ... if at any point you think it has some sort of problem ..bad bearing or whatever .. just pull the belt and fire it up without the belt .. I have even driven home on no belt .. it will not be perfect but it quickly takes it out of the problem list
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Re: Harmonic damper balance weight variations, SBF

Post by MadBill »

Not a Ford guy, but you didn't mention your flywheel's balance. Aren't some also external balance?
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Re: Harmonic damper balance weight variations, SBF

Post by Casper393W »

Was the rotating assembly balanced ? If it is a factory roller block and rotating assembly...it should be 50oz
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Re: Harmonic damper balance weight variations, SBF

Post by SupStk »

Casper393W wrote: Sat May 19, 2018 6:09 pm Was the rotating assembly balanced ? If it is a factory roller block and rotating assembly...it should be 50oz
The aftermarket strokers I've run into are 28 oz. in.
A rotating assembly isn't balanced unless the flywheel/faceplate and damper is part of the assembly.
Seen lots of components out of balance not only for weight but for location. The part at fault could be on either end of the engine.
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Re: Harmonic damper balance weight variations, SBF

Post by cjperformance »

Calypso wrote: Sat May 19, 2018 8:07 am A friend bought a 28oz SBF 302 long block from a reputable builder. Relatively normal performance parts and balanced with the accompanying TCI rattler according to the seller. (Eagle crank, rods, Ross pistons, main cap girdle, Trick Flow hydro roller and heads)

Due to the application, the Rattler could not be utilized as it wasn't the right depth and bolt pattern. It was replaced with Ford performance parts unit with the same balance factor. The engine vibrates noticeably during acceleration. The Rattler has not been messed with in the balance job.

The engine has a small weiand blower, which I'm not familiar with to know If you could test on the engine. That would anyway mean running without blower, alternator and water pump belts.

The next step is to take the dampers to the machine shop to be checked for balance differences. Otherwise there is not much else to do but to take it out, tear it down and send the whole rotating assy to be checked for balance.

The engine didn't come with a flywheel/flexplate.


Anyone seen similar effect from just changing the damper from one manufacturer to another without re-balance? Anything else I could be missing?
Did the long block assembly have an oil pan on /did you see the crank and possibly get the eagle part number off of the crank?
It vibrates on acelleration- im assuming this is as you bring the rpm up with the vehicle stationary and NOT acellerating down the road?
It came with no flex/fly - so it was not balanced after parts manufacture just assembled and theoretically suits 28oz OR at best was balanced to suit thier generic 28oz flex/fly.
Do you definetly have a 28oz flex/fly on it?
I would run it without the blower belt or any acessories then swap the the supplied balancer as a comparison, if it vibrates the same double check your flexplate/fly wheel but chances are that its coming apart, OR you're lucky and the rattler fixes it and you can get your balancer matched.
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Re: Harmonic damper balance weight variations, SBF

Post by Calypso »

Thank you all for your responses.
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Re: Harmonic damper balance weight variations, SBF

Post by Walter R. Malik »

A "Rattler" from TCI is different than most other dampers in the marketplace.
It should not be used for crankshaft balancing; as it says in their own literature.

The crank should be balanced with a known harmonic damper which has the correct weighting, along with the correct flywheel/flexplate.
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Re: Harmonic damper balance weight variations, SBF

Post by cjperformance »

Walter R. Malik wrote: Mon May 21, 2018 1:41 pm A "Rattler" from TCI is different than most other dampers in the marketplace.
It should not be used for crankshaft balancing; as it says in their own literature.

The crank should be balanced with a known harmonic damper which has the correct weighting, along with the correct flywheel/flexplate.
Yes this balance job sounds a bit fishy, O.P. says the rattler wasnt messed with during balancing so either they balanved it to their generic balancer/damper and flexplate combo ans he can get his gear verified OR the balance job is just wrong or not done!
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Re: Harmonic damper balance weight variations, SBF

Post by BillK »

I have found the variation in Ford dampers and flywheels is absolutely terrible. I have a few factory dampers and flexplates I can use as a reference if I think one is way off. Chevy stuff is usually pretty decent, don't know why it seems nobody can get Ford stuff correct. One reason may be the lack of original information. The blueprint specs for the Chevy stuff is available but I have tried on and off for 20 years to find the Ford specs to no avail.

Also, like the others said the rattler cannot be used during balancing. The same goes with the fluid type dampers but at least with those you can take them apart and just use the weighted center hub. I don't know if this is an option with the rattler, I have never seen one.

If he bought it from the original builder he should go ask him. He might have a reference damper that he uses and can match the replacement to it. That would be my first call.
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Re: Harmonic damper balance weight variations, SBF

Post by pdq67 »

Did we figure out if the damper is either the 28 or the 50 oz one?

Before I would tear it down, I would get one of each from a Boneyard and try both to check for vibration.

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